Climbers generally use clean protection devices for two distinct purposes. First, a clean protection device may be used as a form of safety protection for protecting a climber in the event of a fall and second, a clean protection device may intentionally be used to artificially support a climber's weight. Clean protection devices cam or wedge into a crack, hole, gap, orifice, taper, or recess in order to support an outward force. The area or surface within which the clean protection device supports the outward force is considered the protection surface. The protection surface can consist of natural materials such as rock or may consist of artificial materials such as concrete.
Clean protection devices are generally divided into active and passive categories. Passive protection devices include a single object, which contacts the protection surface to support an outward force. For example, a wedge is a passive protection device because it has a single head with a fixed shape. There are numerous types of passive protection devices including nuts, hexes, tri-cams, wedges, rocks, and chocks. Active protection devices include at least two movable objects that can move relative to one another to create a variety of shapes. For example, a slidable chock or slider nut is considered an active protection device because it includes two wedges that move relative to one another to wedge into various shaped crevices. When the two wedges of the slider nut are positioned adjacent to one another, the overall width of the protection device is significantly larger than if the two wedges are positioned on top of one another. The two wedges must make contact with the protection surface in order to actively wedge the device within the protection surface. A further subset of active protection devices is camming devices. These devices translate rotational displacement into linear displacement. Therefore, a slider chock would not be an active camming device because the two wedges simply slide relative to one another and do not rotate. Camming devices include two, three, and four cam lobe devices. The cam lobes on an active camming device are generally spring biased into an expanded position and are able to rotate or pivot about an axle to retract. In operation, at least one cam lobe on either side of the unit must make contact with the protection surface for the device to be able to actively support an outward force. Some active protection devices can also be used passively to support outward forces as well.
Active protection devices are generally preferable to passive protection devices because of their ability to cam into a variety of features. For example, a standard four-cam unit has a particular camming range that allows it to cam into features within a particular size range. Whereas, a passive protection device is limited to a single shape and can therefore only cam or wedge into features that conform to that particular shape. Unfortunately, the largest disadvantage of active protection devices is their considerable head width in relation to passive protection devices. Head width is defined as the maximum distance in the direction of the axle or axles longitudinal axis. Most camming devices contain three or four cam lobes. These cam lobes are typically driven by torsion springs on the axle. The large head width is primary made up of the cam lobes, the torsion springs, and the cable terminal or terminals.
Another advantage of camming devices over passive protection devices is their ability to protect awkward, flaring, and otherwise irregular cracks. This is a result of the cam lobes having independent action allowing them to adjust to the irregularities of the crack.
Traditional active camming devices include camming surfaces which are substantially flat. The camming surface is defined as the portion of the active camming device which engages the crack or recess. Generally, the camming surface is the outer part of one or more cam lobes. Substantially flat camming surfaces are designed to increase friction between the device and the recess within which it is engaged. Friction is necessary between the active camming device and the recess so that the device is not able to slide out. However, some irregularly shaped recesses may cause camming devices with flat camming surfaces to wobble due to a low number of contact points. This wobbling or instability could also cause an active camming device to fail or release from a placement. For at least these reasons, there is a need in the industry for a more stable camming surface design that is applicable to all camming devices.